1. Field of the Invention
The present invention relates to a method and apparatus for image obtainment. More particularly, the present invention relates to a method and apparatus for image obtainment in which light, emitted by a stimulable phosphor sheet due to irradiation thereof by an excitation light, is received.
2. Description of the Related Art
There are known radiation image recordation/reproduction systems in which stimulable phosphors (storable phosphors) that store a portion of radiation energy when irradiation with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.) and emit light corresponding to the energy stored therein when irradiated with an excitation light, such as visible light, are utilized (Japanese Unexamined Patent Publication Nos. 55(1980)-12429, 56(1981)-11395, 56(1981)-11397, etc.). These systems temporarily store radiation image information of a subject such as a human body onto a stimulable phosphor sheet composed of stimulable phosphors arranged in a sheet form, scan the stimulable phosphor sheet with an excitation light thereby generating emitted light, read out the obtained emitted light photoelectrically to obtain image signals, then displays the radiation image of the subject as a visible image on recording media such as photosensitive material, or on a display device such as a CRT based on the image signals.
As an apparatus for photoelectrically reading out the aforementioned emitted light and obtaining an image signal, there is known, for example, an apparatus that employs line sensors of a CCD type, having photoelectric conversion elements consisting of photodiodes arranged in a straight line. This line sensor receives emitted light, generated by the stimulable phosphor sheet with the light receiving surfaces of a plurality of photoelectric conversion elements. Electrical image signals are obtained based on the charge stored in each of the photoelectric conversion elements, and a visible image that represents the radiation image information of the subject recorded on the stimulable phosphor sheet is formed based on these electrical image signals.
The aforementioned line sensors are formed with a light absorption layer covered with metallic film for absorbing white light (i.e., red, green, and blue) in the area surrounding the light receiving surfaces thereof (e.g., a charge transfer path or the like). This is to prevent the generation of false images by noise being mixed in with the image signals. The noise may be signals generated by the emitted light reflected or scattered by a region of the line sensor other than the light receiving surfaces, for example, the charge transfer path, entering the light receiving surfaces.
With regard to the aforementioned radiation image recordation/reproduction system, generally the only light that enters the photoelectric conversion element is the emitted light. Other light, for example, excitation light, is cut off by a filter or the like before entering the photoelectric conversion element. As the wavelength range of the emitted light is included in the wavelength range of blue light, there is a desire for a simpler method of preventing reflection and scattering of the emitted light in the area surrounding the photoelectric conversion elements which does not require covering with a filter that absorbs all of the red, green, and blue light.